Any ideas about no spark

Just reassembled a 1971 Honda ST50 with new coil, ht lead, plug, points, condenser and battery but stil no spark. I am getting an AC output from the alternator that supplies the coil but can't get a spark at all, even with removing the plug cap and holding it close to the engine. I have bought another AC energy transfer coil and still no spark.
Any suggestions of what to look at, I am considering getting a DC coil wired to the battery which might be easier to follow what's wrong.
Any suggestions welcome, thanks.

Coil must be earthed to frame at the 2 bolts that hold coil in place. If the frame has been repainted or powder coated it’s possible the coil does not Earth.

My bike was rebuilt and I didn’t feel like removing engine to get to coil, so I ran new Earth lead from coil bolt to rear light mounting bolt. This is one of the 3 earth connections on the bike, the other being the ignition switch.

Try new Earth...

S

Thanks for the suggestion, the frame has been powder coated, I will run an extra cable to see if that solves the problem.

Thanks again.

Just back in from the garage - jeez it's cold out there. Success! Managed to put 20,000 volts up my arm!

Thanks.

Well that was a brilliant result (not the electric shock), well done

Now starts first kick every time, now discovered the clutch is siezed solid, rolling start to get going for the first time.

Onto the clutch next.....